Health effects unknown for crAssphage found in up to three-quarters of people

A newly discovered virus may already be living in your intestines. As many as three-quarters of people carry this virus, yet it has gone unnoticed until now.

“We haven’t been able to capture the little bugger on a plate and take a picture of it,” says computational biologist Robert Edwards of San Diego State University, who led the study. Instead, the researchers found the new virus by looking at DNA from people’s feces.

The virus went unrecognized for so long because many of its genes don’t resemble those of other known viruses, researchers report July 24 in Nature Communications.

Dubbed crAssphage after the computer program used to discover it, the new virus is a bacteriophage that infects and kills bacteria. It attacks Bacteroides, one of the most common types of friendly bacteria found in people’s intestines. Previous studies have shown that a gut microbe mix containing fewer Bacteroides and more members of another bacteria group, Firmicutes, may promote obesity. It’s not yet clear whether people who carry crAssphage are more prone to obesity because of the virus’s assault on Bacteroides bacteria.